BIOS update ruined dual boot. Cannot rollback.

[Timofeus]

I had a dual boot system with Windows 10 and Debian linux. It worked fine with BIOS ver. F.09.

Recently I made a kind of global s/w and driver update, including updating BIOS to ver. F.36.

After that pc boots only into windows and I'm not able to restore setting in bios where custom .efi file can be choosen - there is only "windows boot manager" available. It is still possible to boot it through F9 menu though.

I tried to roll back to F.09 or F.26 bios, but it is not possible to lower the version with neither boot menu or update program.

Is there a way to restore efi choosing function or a way to roll back to lower BIOS?

[Timofeus]

Okay, looks like there is no way to return to old way of things, but I found sort of workaround in the internets.

You can have a alternative EFI loader working if you replace a microsoft's loader with it in its folder on efi partition.

P.S. A few words personally from me to HP and Insyde:

I don't know what was the purpose of this - to strengthen microsoft's monopoly and force users to quit using other OSs or actually improve security. If latter - you have choosen a pretty **bleep**ty way of improving it. In fact, I see no improvement at all, only new set of useless actions I have to make each time I want to boot non-windows OS.

[Timofeus · Accepted solution]

Update - things return back to normal after update to new grub version. Still unsure what was cause of trouble. Probably a resetting old grub could work too.